Silicon-based ultra-violet LED

ABSTRACT

A light emitting diode (LED), and a method for producing the same. The LED includes a substrate that may be made of silicon, a first conductive layer on one side, and a porous insulating layer on the opposite side. The insulating layer defines microcavities therein, the microcavities having sharp tips on their inner surfaces. The microcavities have gas inside. A second conductive layer is disposed over the insulating layer. When an electrical potential is applied between the conductive layers, the gas-filled microcavities act as plasma discharge lamps, emitting light. The light may be in the ultraviolet portion of the spectrum. The method includes etching a substrate to produce a porous insulating layer on one side, depositing a first conductive layer on the opposite side, and depositing a second conductive layer over the insulating layer. The microcavities in the insulating layer are then filled with gas.

BACKGROUND OF THE INVENTION

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/364,683, filed Mar. 15, 2002 and entitledSILICON-BASED LIGHT EMITTING DIODE, which is in its entiretyincorporated herewith by reference.

[0002] The invention relates to an apparatus and method for emittinglight. The invention also relates more particularly to a silicon-basedlight-emitting diode for emitting light that may include wavelengths inthe ultraviolet portion of the electromagnetic spectrum.

[0003] Light emitting diodes, or LEDs, are known per se. ConventionalLEDs utilize the semiconducting properties of materials such as silicon.

[0004] In a conventional LED, light is generated when free electronsdrop from the conduction band of a semiconducting diode into energyholes. Each such event releases energy in the form of a photon, with thewavelength of the photondepending upon the energy gap between theconduction band and the holes. As the energy gap becomes larger, thephotons released likewise become more energetic. The more energy anindividual photon has, the shorter its wavelength.

[0005] The principles governing the operation of conventional LEDs arewell known, and are not further described herein.

[0006] However, known LEDs suffer from several limitations.

[0007] For example, the wavelengths that may be produced are limited bythe magnitude of the energy gap. The shorter the wavelength of lightthat is to be emitted, the larger the energy gap must be. It istherefore particularly difficult to produce light with shortwavelengths, in particular ultraviolet light, using known LEDs. Inprinciple, it is possible to produce a semiconducting LED with an energygap large enough that it emits ultraviolet light, i.e. light having awavelength of less than about 400 nm. However, such LEDs are difficultto produce, expensive, and inefficient.

[0008] Indeed, silicon-based LEDs are extremely inefficient emitters oflight in general. The best reported efficiency for a silicon-based LEDof conventional design is 0.8%. That is, no more than 0.8% of the energyapplied to that LED is emitted as light, the remainder typically beinglost as heat.

SUMMARY OF THE INVENTION

[0009] It is the purpose of the present invention to overcome thesedifficulties, thereby providing an improved apparatus and method forgenerating light, including but not limited to ultraviolet light.

[0010] It is more particularly the purpose of the present invention toprovide an LED that is suited for producing light in wavelengths thatmay include the ultraviolet portion of the electromagnetic spectrum, anda method for producing the same.

[0011] An embodiment of an LED in accordance with the principles of thepresent invention includes a substrate. A first conductive layer isdisposed on a first side of the substrate.

[0012] An insulating layer is disposed on a second side of thesubstrate. The insulating layer defines a plurality of microcavitiestherein. The microcavities have small points, referred to herein asasperites, on their surfaces. In addition, the microcavities contain gastherein.

[0013] A second conductive layer is disposed over the insulating layer.The second conductive layer is transparent to radiation of the frequencythat the diode emits.

[0014] When an electrical potential is applied between the firstconductive layer and the second conductive layer, the microcavities inthe insulating layer act as tiny gas discharge lamps.

[0015] This occurs because the high electrical resistance of theinsulating layer allows strong electric fields to develop within themicrocavities. As these strong electric fields develop, the sharp tipsof the asperites begin to eject electrons, ionizing the gas present inthe microcavities. The gas transforms into plasma, which radiates lightat one or more plasma emission lines.

[0016] By controlling the physical properties of the device, i.e. thecomposition and pressure of the gas in the microcavities, it is possibleto control the frequency of the light emitted. For example, under theproper conditions, the light is in the ultraviolet portion of thespectrum.

[0017] It is emphasized that an LED in accordance with the principles ofthe present invention does not rely on semiconductive properties such aselectron transport.

[0018] It is furthermore emphasized that although particular embodimentsof an LED in accordance with the principles of the claimed invention mayproduce ultraviolet light, the invention is not limited only toembodiments that produce ultraviolet light. Other embodiments mayproduce other wavelengths.

[0019] An LED in accordance with the principles of the present inventionmay be incorporated into an LED assembly.

[0020] An LED assembly in accordance with the principles of the presentinvention includes an LED, with an encapsulation enclosing it. Theencapsulation has a window that is transparent to the wavelength of thelight that is emitted by the LED. The assembly also includes first andsecond contact pins that are electrically connected to the first andsecond conductive layers. Thus, an electrical potential applied to thecontact pins causes an electrical potential to be applied to the firstand second conductive layers, so that the LED then emits light.

[0021] In a method for producing an LED in accordance with theprinciples of the present invention, a suitable substrate is provided. Afirst conductive layer is applied to a first side of the substrate.

[0022] The second side of the substrate is etched to form an insulatinglayer with microcavities therein, the microcavities having asperites.

[0023] A second conductive layer, transparent to radiation of thewavelength that the LED is to produce, is applied over the insulatinglayer.

[0024] The microcavities are impregnated with gas.

[0025] An LED in accordance with the principles of the present inventionmay be incorporated into an LED assembly.

[0026] In a method for producing an LED assembly in accordance with theprinciples of the present invention, an LED is provided.

[0027] The LED is encapsulated with an encapsulation. The encapsulationhas a window that is transparent to radiation of the wavelength emittedby the LED.

[0028] A first contact pin is connected electrically to the firstconductive layer, and a second contact pin is connected electrically tothe second conductive layer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Like reference numbers generally indicate corresponding elementsin the figures. Unless otherwise specified herein, these figures are notto scale.

[0030]FIG. 1 shows a schematic cross-section of an embodiment of a lightemitting diode in accordance with the principles of the presentinvention.

[0031]FIG. 2 shows an enlarged view of a microcavity of the LED shown inFIG. 1.

[0032]FIG. 3 shows a schematic cross-section of an embodiment of an LEDassembly in accordance the principles of the present invention.

[0033]FIG. 4 shows an LED at a point in its production using a method inaccordance with the principles of the present invention.

[0034]FIG. 5 shows the LED of FIG. 4 at a later point in its production.

[0035]FIG. 6 shows the LED of FIG. 5 at a later point in its production.

[0036]FIG. 7 shows an embodiment of an arrangement for producing aninsulating layer with microcavities therein in accordance with theprinciples of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0037] Referring to FIG. 1, an embodiment of an light emitting diode(LED) 10 in accordance with the principles of the present invention isshown therein.

[0038] The LED 10 includes a substrate 12.

[0039] A first electrically conductive layer 14 is disposed on a firstside of the substrate 12.

[0040] An electrically insulating layer 16 is disposed on a second sideof the substrate 12, opposite the first conductive layer 14. Theinsulating layer 16 defines a plurality of tiny cavities therein,hereinafter referred to as microcavities 18.

[0041] As illustrated in FIG. 2, the microcavities 18 include sharp tipstherein, hereinafter referred to as asperites 20.

[0042] Returning to FIG. 1, a second electrically conductive layer 22 isdisposed over the insulating layer 16.

[0043] The substrate 12 may be made from a variety of materials. In apreferred embodiment, the substrate 12 may comprise silicon. In a morepreferred embodiment, the substrate 12 may comprise single-crystalsilicon. In a still more preferred embodiment, the substrate 12 maycomprise 100 direction type n⁺silicon. In a yet more preferredembodiment, the substrate 12 may be doped with antimony.

[0044] Such compositions are particularly suitable insofar as the use ofsilicon substrates in electronic devices is well-established andwell-understood. However, the above compositions are exemplary only. Awide variety of alternative materials may be equally suitable for use asthe substrate 12.

[0045] Substrates, in particular silicon substrates, are well known perse, and are not described further herein.

[0046] It is emphasized that although silicon is widely used for itssemiconductive properties, the present invention does not rely onsemiconduction, and does not require a substrate 12 that issemiconductive.

[0047] Rather, it is the classical resistance of the substrate 12 thatis of significance to the present invention. In a preferred embodiment,the substrate 12 has an electrical resistivity of 0.008 to 0.09 Ω-cm.More preferably, the substrate 12 has an electrical resistivity of 0.008to 0.02 Ω-cm.

[0048] The first conductive layer 14 may be made of any reasonablyconductive material, including but not limited to metals and conductivepolymers. In a preferred embodiment, the first conductive layer 14comprises aluminum. However, this is exemplary only, and otherconductive materials may be equally suitable.

[0049] The thickness of the first conductive layer 14 is sufficient toenable good electrical conductivity. It will be appreciated by those ofskill in the art that the precise thickness of the first conductivelayer 14 that is necessary depends on the material that is used for thefirst conductive layer 14.

[0050] For example, when the first conductive layer 14 is composed ofaluminum or a material with similar electrical properties, a thicknessof 0.25 to 1 μm may be sufficient for the first conductive layer 14.More preferably, the thickness may be 0.3 to 0.4 μm. However, thesethicknesses are exemplary only, and different thicknesses may be equallysuitable.

[0051] The insulating layer 16 comprises a material that is transparentto light of the wavelength that is to be emitted by the LED 10. However,because the insulating layer 16 is porous, with a portion of its volumebeing microcavities 18, it may be suitable to use materials for theinsulating layer 16 that, when solid, would be poor transmitters oflight.

[0052] Like the substrate 12, the insulating layer 16 may be made from avariety of materials. In a preferred embodiment, the insulating layer 16may comprise silicon. In a more preferred embodiment, the insulatinglayer 16 may comprise single-crystal silicon. In a still more preferredembodiment, the insulating layer 16 may comprise 100 direction type n⁺silicon. In a yet more preferred embodiment, the insulating layer 16 maybe doped with antimony.

[0053] However, the above compositions are exemplary only. A widevariety of alternative materials may be equally suitable for use as theinsulating layer 16.

[0054] As noted with regard to the substrate 12, the present inventiondoes not rely on semiconduction, and does not require an insulatinglayer 16 that is semiconductive.

[0055] In a preferred embodiment, the insulating layer 16 is formed fromthe same material as the substrate 12. In a more preferred embodiment,the insulating layer 16 is formed from a portion of the substrate 12.

[0056] It will be appreciated by those of skill in the art that theprecise thickness of the insulating layer 16 that is necessary dependson the material that is used for the insulating layer 16.

[0057] For example, when the insulating layer 16 is composed of silicon,a thickness of 0.7 to 2.5 μm may be suitable for the insulating layer16. More preferably, the thickness may be 1 to 2 μm. However, thisthickness is exemplary only, and different thicknesses may be equallysuitable.

[0058] As noted above, the insulating layer 16 is porous, and defines aplurality of microcavities 18 therein.

[0059] For clarity, the microcavities 18 are illustrated in FIG. 1 asbeing spherical, closed, and arranged in an orderly pattern. Althoughthey are so illustrated for purposes of clarity, this is exemplary only.

[0060] It is not necessary for the microcavities 18 to be spherical. Avariety of other shapes, including but not limited to cylinders ortubes, and amorphous “blobs”, may be equally suitable. It is also notedthat different microcavities 18 may have different shapes within thesame insulating layer 16.

[0061] Likewise, it is not necessary for the microcavities 18 to beclosed off from one another. Microcavities 18 that are interconnectedmay be equally suitable.

[0062] Furthermore, it is not necessary for the microcavities 18 to bedistributed in a regular or orderly pattern. For certain embodiments itis preferable that the microcavities 18 are spread in a substantiallyuniform manner across the area of the insulating layer 16. However, arandom or chaotic distribution of microcavities 18 within the insulatinglayer 16 may be equally suitable as an ordered arrangement.

[0063] As may be seen in FIG. 2, the microcavities 18 include asperites20 therein. The asperites 20 are sharp tips on the surfaces of themicrocavities 18.

[0064] As illustrated, the asperites 20 are discrete, conical points.However, this is exemplary only. A wide variety of shapes of asperites20 may be equally suitable. It is only necessary that they include somerelatively sharp edge or point, so as to facilitate the discharge of anelectric field as described below.

[0065] Likewise, it is not necessary that each microcavity 18 containexactly two asperites 20, or that asperites 20 be arranged at oppositeends of a microcavity 18. Although this arrangement is illustrated forclarity, it is exemplary only, and other numbers and arrangements ofasperites 20 may be equally suitable.

[0066] The microcavities 18 have a gas therein. The gas is one that issuitable for producing light via a plasma discharge when an electriccurrent flows therethrough.

[0067] A wide variety of gases are suitable for use in the presentinvention. Suitable gases include, but are not limited to, nitrogen,xenon, and argon. The gases need not be pure; mixtures of two or moregases may also be suitable.

[0068] A variety of pressures of gas within the microcavities 18 may besuitable. The pressure of the gas depends at least in part upon thespecific physical properties of the embodiment of the LED 10 inquestion, i.e. the type of gas used, the size, shape, and distributionof microcavities 18 and asperites 20, the dimensions, composition, andresistivity of the insulating layer 16, etc.

[0069] For example, for certain preferred embodiments, a gas pressure of1 to 100 mbar of nitrogen is suitable. However, this is exemplary only,and other gas pressures may be equally suitable.

[0070] Referring again to FIG. 1, the second conductive layer 22 may bemade of any reasonably conductive material, including but not limited tometals and conductive polymers. In a preferred embodiment, the secondconductive layer 22 comprises an alloy of gold and copper. In a morepreferred embodiment, the second conductive layer 22 comprises an alloyof gold and copper in a ratio of 9:1 to 3:2. In a still more preferredembodiment, the second conductive layer 22 comprises an alloy of goldand copper in a ratio of 4:1 to 7:3. However, this is exemplary only,and other conductive materials may be equally suitable.

[0071] The thickness of the second conductive layer 22 is sufficient toenable good electrical conductivity. It will be appreciated by those ofskill in the art that the precise thickness of the second conductivelayer 22 that is necessary depends on the material that is used for thesecond conductive layer 22.

[0072] The second conductive layer 22 is transparent to light of thewavelength that is to be emitted by the LED. For certain materials,including but not limited to metals, this requirement may also helpdetermine the suitable thickness of the second conductive layer 22.

[0073] For example, when the second conductive layer 22 is composed ofan alloy of gold and copper in a ratio of 4:1 to 7:3 or a material withsimilar electrical and optical properties, a thickness of 20 to 100 nmmay be suitable for the second conductive layer 22. More preferably, thethickness may be 30 to 60 nm. It is noted that the gold and copper alloyin question is transparent to certain wavelengths of light, includingultraviolet light, when applied in these thicknesses. However, thesethicknesses are exemplary only, and different thicknesses may be equallysuitable.

[0074] When an electrical potential is applied between the first andsecond conductive layers 14 and 22, the relatively high resistivity ofthe insulating layer 16 prevents the free flow of current therebetween.This results in the growth of strong electric fields within theinsulating layer 16.

[0075] In particular, strong electric fields form within themicrocavities 18. If the microcavities 18 were generally smooth, theelectric fields might eventually stabilize. However, the sharp tips ofthe asperites 20 within the microcavities 18 results in localdiscontinuities in the electric fields. At some point, the electricfields in a given microcavity 18 collapse, whereupon the asperites 20therein inject streams of electrons from their sharp tips into themicrocavity 18.

[0076] This sudden electrical discharge ionizes the gas within themicrocavity 18 into a plasma by stripping away one or more electronsfrom the gas atoms. When the freed electrons in the plasma recombinewith the gas atoms, the gases emit radiation at characteristicwavelengths that depend upon the type of gas present in the microcavity.

[0077] For example, for nitrogen, radiation with a wavelength ofapproximately 337.1 nm is emitted. It is noted that this wavelength isin the ultraviolet portion of the electromagnetic spectrum. However,this is exemplary only, and embodiments of the present invention thatemit other wavelengths may be equally suitable. In particular,embodiments that produce one or more wavelengths of ultravioletradiation between 200 and 400 nm may be equally suitable. Embodimentsthat produce light at one or more wavelengths that are not in theultraviolet portion of the electromagnetic spectrum may also be equallysuitable.

[0078] So long as an electrical potential continues to be applied, theelectric field within the microcavity 18 will regenerate after eachcollapse, and the process will repeat.

[0079] In other words, the microcavities 18 act as a plurality of tinyplasma discharge lamps. The operational principles of plasma dischargelamps are well known per se, and are not described further herein.

[0080] It is noted that the various microcavities 18 will notnecessarily discharge in unison, nor is it necessary that they do so.Furthermore, it is not even necessary that all of the microcavities 18that are present within a given insulating layer 16 discharge at all, solong as at least some do so.

[0081] The electric potential between the first and second conductivelayers 14 and 22 is sufficient to generate electric fields that buildand collapse in at least a significant portion of the microcavities 18.In a preferred embodiment, the electric potential may need be no morethan approximately 20 volts. In a more preferred embodiment, theelectric potential may need be no more than approximately 10 volts.

[0082] Turning to FIG. 3, an embodiment of an LED assembly 30 inaccordance with the principles of the present invention is showntherein.

[0083] The LED assembly 30 includes an LED in accordance with theprinciples of the claimed invention, similar to the LED 10 shown in FIG.1.

[0084] The LED assembly thus includes a substrate 12, a firstelectrically conductive layer 14 is disposed on a first side of thesubstrate 12, and an electrically insulating layer 16 is disposed on asecond side of the substrate 12. The insulating layer 16 defines aplurality of microcavities 18 therein, with asperites 20. A secondelectrically conductive layer 22 is disposed over the insulating layer16.

[0085] In addition, the LED assembly 30 includes an encapsulation 32,which encapsulates the substrate 12, first electrically conductive layer14, electrically insulating layer 16, and second electrically conductivelayer 22.

[0086] The encapsulation 32 includes a window 34 that is transparent tolight of the wavelength that the LED emits.

[0087] The encapsulation 32 encapsulates the LED, both to protect theLED, and also to protect persons or structures that come in contact withit from damage that might be caused by electric potential, plasmaemission, etc.

[0088] In addition, certain embodiments of encapsulation 32 may act as abarrier between the microcavities 18 and the outside atmosphere, inorder to reduce any exchange of gas between the atmosphere and themicrocavities 18 that might degrade the performance of the LED. In thoseembodiments, the encapsulation may be gas-tight.

[0089] The LED assembly 30 also includes a first contact pin 36 that isin electrical contact with the first conductive layer 14, and a secondcontact pin 38 that is in contact with the second conductive layer 22.

[0090] Thus, an electrical potential that is applied between the firstand second contact pins 36 and 38 results in a similar electricalpotential being applied between the first conductive layer 14 and thesecond conductive layer 22.

[0091] It is emphasized that incorporating the LED 10 previously shownand described into the LED assembly 30 is exemplary only. For certainapplications, it may be equally suitable to incorporate an LED 10 inaccordance with the principles of the present invention into otherassemblies, or to use it as a stand-alone device.

[0092] A variety of materials may be suitable for use as theencapsulation 32. Suitable materials include, but are not limited to,plastics.

[0093] A variety of materials likewise may be suitable for use as thewindow 34. Suitable materials include, but are not limited to, glasstransparent to light of the wavelength emitted by the LED.

[0094] Similarly, a variety of materials may be suitable for use as thefirst and second contact pins 36 and 38. In a preferred embodiment, thefirst and second contact pins 36 and 38 are made of metal wire. However,this is exemplary only, and other materials may be equally suitable.

[0095] It is noted that, although only two contact pins 36 and 38 areshown, it may be equally suitable for certain embodiments to includeadditional contact pins.

[0096] As illustrated in FIG. 3, the second contact pin 38 passesthrough the first conductive layer 14, the substrate 12, and theinsulating layer 16 to reach the second conductive layer 22. As shown,in order to prevent short circuits (i.e. between the second contact pin38 and the first conductive layer 14), the LED assembly 30 may includeinsulation 40 to isolate the second contact pin 38.

[0097] However, this is exemplary only. For certain embodiments, it maynot be necessary to use insulation 40 to isolate the second contact pin38. For example, the second contact pin 38 may be connected to thesecond conductive layer 22 in such a way that it does not contact thefirst conductive layer 14. One exemplary arrangement is to connect thesecond contact pin 38 directly to the second conductive layer 22 withoutpassing through other portions of the LED. Another exemplary arrangementis to prepare an aperture in the first conductive layer 14 proximate thelocation of the second contact pin 38, so as to avoid contacttherebetween. Other embodiments may likewise be suitable.

[0098] FIGS. 4-6 show an LED similar to the LED 10 illustrated in FIG.1, at several points in an exemplary production process.

[0099] As shown in FIG. 4, the exemplary process begins with a substrate12. Methods for producing substrates, in particular silicon substrates,are well known per se, and are not described further herein.

[0100] As shown in FIG. 5, an insulating layer 16 is then formed on thesubstrate 12. The insulating layer has microcavities 18 and asperites 20therein.

[0101] As may be seen from a comparison of FIGS. 4 and 5, in theexemplary process illustrated therein the insulating layer 16 is formedfrom a portion of the substrate 12. However, this is exemplary only, andother methods, including but not limited to forming an insulating layer16 separately and applying it to the substrate 12, may be equallysuitable.

[0102] One exemplary method for producing the insulating layer 16 withthe microcavities 18 and the asperites 20 therein is toelectrochemically etch the substrate 12, so as to render a portion ofthe substrate 12 porous.

[0103] Referring to FIG. 7, an exemplary arrangement forelectrochemically etching the substrate 12 is shown therein.

[0104] As illustrated in FIG. 7, the substrate 14 with the firstconductive layer 12 disposed therein is placed in a bath of etchant 50.

[0105] The substrate 14 is connected electrically to a power supply 54.As shown, the substrate is connected to the positive terminal of thepower supply 54, and so acts as the anode.

[0106] A cathode 52 is also placed in the etchant 50, and is connectedto the negative terminal of the power supply 54. In order to facilitatemonitoring of the etching process, an ammeter 52 may be connectedbetween the cathode 52 and the power supply 54. However, this isexemplary only.

[0107] The composition of the cathode depends at least in part on theetching conditions and the type of etchant 50 used. For example, aplatinum cathode is suitable for many types of electrochemical etchingoperations, as it is highly conductive, heat tolerant, and highlyresistant to corrosion. However, this is exemplary only, and other typesof cathode may be equally suitable.

[0108] A variety of etchants 50 and etching conditions may be suitablefor performing electrochemical etching of the substrate 12. It will beappreciated by those of skill in the art that the particular conditionsand etchants 50 will vary depending on such factors as the material usedto form the substrate 12.

[0109] For example, for a substrate 12 comprised of silicon, a preferredembodiment of an etching step may use an etchant 50 comprising anethanoic hydrogen fluoride solution. In a more preferred embodiment, theetchant might have a concentration of 10% to 25%. In a still morepreferred embodiment, the etchant might have a concentration of 24%.

[0110] Likewise, for a substrate 12 comprised of silicon, a preferredembodiment of an etching step may include etching with a current densityof 1 to 4 mA/cm². In a more preferred embodiment, the current densitymay be 2 mA/cm².

[0111] Similarly, for a substrate 12 comprised of silicon, a preferredembodiment of an etching step may last for from 5 to 30 minutes. In amore preferred embodiment, etching may last for from 10 to 15 minutes.

[0112] In addition, for certain embodiments, it may be preferable toapply a resist to some or all of the substrate 12, and/or any otherelements of the LED 10 that are present during etching in order tocontrol the portions that are etched.

[0113] However, these parameters are exemplary only, and other etchantsand other etching conditions may be equally suitable.

[0114] Furthermore, the use of an electrochemical etching step is itselfexemplary only. Other steps for producing an insulating layer 16 withmicrocavities 18 and asperites 20 therein may be equally suitable.

[0115] In some embodiments of a method according to the principles ofthe present invention wherein the insulating layer 16 is formed byetching the substrate 12, it may be preferable to heat the substrate 12prior to etching in order to drive off impurities within or on thesurface of the substrate 12 that might interfere with etching.

[0116] For example, for certain embodiments, heating the substrate 12 toa temperature of 200 to 300° C., for a duration of 30±6 minutes may besuitable. Furthermore, for certain embodiments, heating the substrate 12while it is in a vacuum may also be suitable.

[0117] However, heating the substrate prior to etching is exemplaryonly.

[0118] As shown in FIG. 6, a first conductive layer 14 is then appliedto a first side of the substrate 12.

[0119] A variety of methods may be used to apply the first conductivelayer 14 to the substrate 12. It will be appreciated by those of skillin the art that the methods suitable for applying the first conductivelayer 14 depend at least in part on the particular materials used in thefirst conductive layer 14.

[0120] For example, when the first conductive layer 14 is composed ofaluminum, suitable methods may include, but are not limited to,electroplating, vapor deposition, and sputtering. These methods areexemplary only, and different methods may be equally suitable.

[0121] In addition, in the exemplary method described herein, a secondconductive layer 22 is formed over the insulating layer 16.

[0122] A variety of methods may be used to apply the second conductivelayer 22 to the insulating layer 16. It will be appreciated by those ofskill in the art that the methods suitable for applying the secondconductive layer 22 depend at least in part on the particular materialsused in the second conductive layer 22.

[0123] For example, when the second conductive layer 22 is composed ofan alloy of gold and copper, suitable methods may include, but are notlimited to, electroplating, vapor deposition, and sputtering. Thesemethods are exemplary only, and different methods may be equallysuitable.

[0124] When the second conductive layer 22 is applied, the resulting LEDresembles that illustrated in FIG. 1.

[0125] According to this exemplary method, once the solid structure ofthe LED is complete, gas is introduced into the microcavities 18.

[0126] A variety of methods may be used to introduce gas into themicrocavities 18. For example, for certain embodiments, impregnating themicrocavities 18 by surrounding the LED with gas may be suitable. In apreferred embodiment, the microcavities 18 are impregnated to a pressureof 1 to 100 mbar for a duration of 30±6 minutes.

[0127] In addition, in certain embodiments of the method it may besuitable to heat the LED while impregnating the microcavities 18 withgas. In a preferred embodiment, the LED is heated to 100 to 150° C.while impregnating the microcavities 18 with gas.

[0128] However, these conditions and methods for introducing gas intothe microcavities are exemplary only. Other conditions and other methodsmay be equally suitable.

[0129] It is noted that, although FIGS. 4-6 and the preceding textprovide a description of an exemplary method of producing an LED that isin accordance with the principles of the claimed invention, this method,and in particular the order of the steps as described, is exemplaryonly.

[0130] For example, although the addition of the first conductive layeris described after the addition of the insulating layer, for certainembodiments it may be equally suitable to form the insulating layerafter forming the first conductive layer.

[0131] Thus, the order of the steps as described is exemplary only, andother arrangements may be equally suitable.

[0132] A method of producing an LED assembly in accordance with theprinciples of the present invention may be used to produce an LED 30similar to that shown in FIG. 3.

[0133] An LED having a substrate 12, a first electrically conductivelayer 14, an electrically insulating layer 16 with a plurality ofmicrocavities 18 and asperites 20 therein, and a second electricallyconductive layer 22 is encapsulated in an encapsulation 32.

[0134] The encapsulation 32 includes a window 34 that is transparent toradiation of the wavelengths produced by the LED.

[0135] A variety of methods of forming the encapsulation 32 and thewindow 34 may be suitable.

[0136] A first contact pin 36 is connected electrically with the firstconductive layer 14, and a second contact pin 38 is connectedelectrically with the second conductive layer 22, so that an electricalpotential applied between the first and second contact pins 36 and 38produces a similar electrical potential between the first conductivelayer 14 and the second conductive layer 22.

[0137] A variety of methods of connecting the first and second contactpins 36 and 38 may be suitable. Suitable methods include, but are notlimited to, the use of a conductive adhesive between a contact pin 36,38 and its corresponding conductive layer 14, 22.

[0138] The above specification, examples and data provide a completedescription of the manufacture and use of the composition of theinvention. Since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the invention, the inventionresides in the claims hereinafter appended.

We claim:
 1. A light emitting diode, comprising: a substrate; a firstconductive layer disposed on a first side of said substrate; aninsulating layer disposed on a second side of said substrate, saidinsulating layer defining a plurality of microcavities therein, saidcavities comprising asperites, said microcavities having a gas therein;and a second conductive layer disposed on said insulating layer; whereinwhen an electrical potential is applied between said first conductivelayer and said second conductive layer, said gas forms a plasma thatemits radiation in the electromagnetic spectrum; and said secondconductive layer is transparent to said radiation.
 2. The light emittingdiode according to claim 1, wherein: said substrate comprises silicon.3. The light emitting diode according to claim 2, wherein: saidsubstrate is doped with antimony.
 4. The light emitting diode accordingto claim 2, wherein: said substrate comprises silicon (100), type n⁺. 5.The light emitting diode according to claim 1, wherein: said substratehas a resistivity of 0.008 to 0.09 Ω-cm.
 6. The light emitting diodeaccording to claim 1, wherein: said substrate has a resistivity of 0.008to 0.02 Ω-cm.
 7. The light emitting diode according to claim 1, wherein:said first conductive layer comprises metal.
 8. The light emitting diodeaccording to claim 7, wherein: said first conductive layer comprisesaluminum.
 9. The light emitting diode according to claim 1, wherein:said first conductive layer has a thickness of 0.25 to 1 μm.
 10. Thelight emitting diode according to claim 1, wherein: said firstconductive layer has a thickness of 0.3 to 0.4 μm.
 11. The lightemitting diode according to claim 1, wherein: said insulating layercomprises silicon.
 12. The light emitting diode according to claim 11,wherein: said insulating layer is doped with antimony.
 13. The lightemitting diode according to claim 11, wherein: said insulating layercomprises silicon (100), type n⁺.
 14. The light emitting diode accordingto claim 1, wherein: said insulating layer has a resistivity of 0.008 to0.09 Ω-cm.
 15. The light emitting diode according to claim 1, wherein:said insulating layer has a resistivity of 0.008 to 0.02 Ω-cm.
 16. Thelight emitting diode according to claim 1, wherein: said insulatinglayer and said substrate comprise identical materials.
 17. The lightemitting diode according to claim 1, wherein: said insulating layer hasa thickness of 0.7 to 2.5 μm.
 18. The light emitting diode according toclaim 1, wherein: said insulating layer has a thickness of 1 to 2 μm.19. The light emitting diode according to claim 1, wherein: said gas insaid microcavities comprises at least one of the group consisting ofnitrogen, xenon, and argon.
 20. The light emitting diode according toclaim 1, wherein: said gas in said microcavities has a pressure of 1 to100 mbar.
 21. The light emitting diode according to claim 1, wherein:said second conductive layer comprises metal.
 22. The light emittingdiode according to claim 21, wherein: said second conductive layercomprises an alloy of gold and copper.
 23. The light emitting diodeaccording to claim 22, wherein: said alloy has a gold:copper ratio of9:1 to 3:2.
 24. The light emitting diode according to claim 22, wherein:said alloy has a gold:copper ratio of 4:1 to 7:3.
 25. The light emittingdiode according to claim 1, wherein: said second conductive layer has athickness of 20 to 100 nm.
 26. The light emitting diode according toclaim 1, wherein: said second conductive layer has a thickness of 30 to60 nm.
 27. The light emitting diode according to claim 1, wherein: saidelectrical potential is not more than approximately 20 volts.
 28. Thelight emitting diode according to claim 1, wherein: said electricalpotential is not more than approximately 10 volts.
 29. The lightemitting diode according to claim 1, wherein: said radiation has awavelength of 200 to 400 nm.
 30. The light emitting diode according toclaim 1, wherein: said radiation has a wavelength of 337.1 nm.
 31. AnLED assembly, comprising: a light emitting diode, said diode comprising:a substrate; a first conductive layer disposed on a first side of saidsubstrate; an insulating layer disposed on a second side of saidsubstrate, said insulating layer defining a plurality of microcavitiestherein, said cavities comprising asperites, said microcavities having agas therein; and a second conductive layer disposed on said insulatinglayer; wherein when an electrical potential is applied between saidfirst conductive layer and said second conductive layer, said gas formsa plasma that emits radiation in the electromagnetic spectrum; and saidsecond conductive layer is transparent to said radiation; anencapsulation encapsulating said diode, said encapsulation comprising awindow transparent to said radiation; and first and second contact pins,said first contact pin being in electrical contact with said firstconductive layer, and said second contact pin being in electricalcontact with said second conductive layer.
 32. The LED assemblyaccording to claim 31, wherein: said encapsulation is gas-tight.
 33. TheLED assembly according to claim 31, wherein: said window is transparentto radiation between 200 and 400 nm in wavelength.
 34. The LED assemblyaccording to claim 31, wherein: said window has a transmittance of atleast 90%.
 35. The LED assembly according to claim 31, wherein: saidcontact pins are bonded to said conductive layers with conductiveadhesive.
 36. A method for producing an light emitting diode, comprisingthe steps of: providing a substrate; forming an insulating layer on saidsubstrate defining microcavities therein, said microcavities comprisingasperites; applying a first conductive layer to a side of said substrateopposite said insulating layer; applying a second conductive layer onsaid insulating layer, said second conductive layer being transparent toelectromagnetic radiation; and impregnating said microcavities with agas.
 37. The method according to claim 36, wherein: said substratecomprises silicon.
 38. The method according to claim 37, wherein: saidsubstrate is doped with antimony.
 39. The method according to claim 37,wherein: said substrate comprises silicon (100), type n⁺.
 40. The methodaccording to claim 36, wherein: said substrate has a resistivity of0.008 to 0.09 Ω-cm.
 41. The method according to claim 36, wherein: saidsubstrate has a resistivity of 0.008 to 0.02 Ω-cm.
 42. The methodaccording to claim 36, wherein: said insulating layer is formed byetching said substrate.
 43. The method according to claim 42, wherein:said insulating layer is formed by electrochemical etching.
 44. Themethod according to claim 43, wherein: said electrochemical etching isconducted using an ethanoic hydrogen fluoride solution.
 45. The methodaccording to claim 44, wherein: said ethanoic hydrogen fluoride solutionhas a concentration of 10% to 25%.
 46. The method according to claim 44,wherein: said ethanoic hydrogen fluoride solution has a concentration of24%.
 47. The method according to claim 43, wherein: said insulatinglayer is formed using a current density of 1 to 4 mA/cm².
 48. The methodaccording to claim 43, wherein: said insulating layer is formed using acurrent density of 2 mA/cm².
 49. The method according to claim 43,wherein: said substrate is etched for from 5 to 30 minutes.
 50. Themethod according to claim 43, wherein: said substrate is etched for from10 to 15 minutes.
 51. The method according to claim 43, wherein: whereinsaid substrate serves as an anode during etching, and platinum is usedas a cathode during etching.
 52. The method according to claim 36,wherein: said first conductive layer comprises metal.
 53. The methodaccording to claim 52, wherein: said first conductive layer comprisesaluminum.
 54. The method according to claim 36, wherein: said secondconductive layer comprises metal.
 55. The method according to claim 36,wherein: said second conductive layer comprises an alloy of gold andcopper.
 56. The method according to claim 55, wherein: said alloy has agold:copper ratio of 9:1 to 3:2.
 57. The method according to claim 56,wherein: said alloy has a gold:copper ratio of 4:1 to 7:3.
 58. Themethod according to claim 36, wherein: said second conductive layer hasa thickness of 20 to 100 nm.
 59. The method according to claim 36,wherein: said second conductive layer has a thickness of 30 to 60 nm.60. The method according to claim 36, wherein: said gas comprises atleast one of the group consisting of nitrogen, xenon, and argon.
 61. Themethod according to claim 36, wherein: said microcavities areimpregnated to a pressure of 1 to 100 mbar.
 62. The method according toclaim 36, wherein: said microcavities are impregnated with said gas at atemperature of 100 to 150° C.
 63. The method according to claim 36,wherein: said microcavities are impregnated with said gas for 24 to 36minutes.
 64. The method according to claim 42, further comprising thestep of: before said substrate is etched, heating said substrate. 65.The method according to claim 64, wherein: said substrate is heated invacuum.
 66. The method according to claim 64, wherein: said substrate isheated at a temperature of 200 to 300° C.
 67. The method according toclaim 64, wherein: said substrate is heated for 24 to 36 minutes.
 68. Amethod for producing an LED assembly, comprising the steps of: producinga light emitting diode by: providing a substrate; applying a firstconductive layer to a first side of said substrate; etching a secondside of said substrate so as to form an insulating layer definingmicrocavities therein, said microcavities comprising asperites; applyinga second conductive layer on said insulating layer, said secondconductive layer being transparent to electromagnetic radiation; andimpregnating said microcavities with a gas; encapsulating said diode inan encapsulation, said encapsulation comprising a window transparent toelectromagnetic radiation; and electrically connecting a first contactpin to said first conductive layer and a second contact pin to saidsecond conductive layer.
 69. The method according to claim 68, wherein:said encapsulation is gas-tight.
 70. The method according to claim 68,wherein: said window is transparent to radiation between 200 and 400 nmin wavelength.
 71. The method according to claim 68, wherein: saidwindow has a transmittance of at least 90%.
 72. The method according toclaim 68, wherein: said contact pins are bonded to said conductivelayers with conductive adhesive.
 73. A method for producing light,comprising the steps of: providing a substrate; applying a firstconductive layer to a first side of said substrate; etching a secondside of said substrate so as to form an insulating layer definingmicrocavities therein, said microcavities comprising asperites; applyinga second conductive layer on said insulating layer; impregnating saidmicrocavities with a gas; and applying an electrical potential betweensaid first conductive layer and said second conductive layer such thatsaid gas forms a plasma that emits radiation in the electromagneticspectrum.
 74. The light emitting diode according to claim 31, wherein:said radiation has a wavelength between 200 and 400 nm.
 75. The methodaccording to claim 36, wherein: said second conductive layer istransparent to radiation between 200 and 400 nm in wavelength.
 76. Themethod according to claim 68, wherein: said second conductive layer istransparent to radiation between 200 and 400 nm in wavelength.